Make compare button URL aware if current repo is a fork (#2162) (#2163)

* Make compare button URL aware if current repo is a fork (#2162)

* Optimize code

* To not change current behaviour check if signed in user has fork of base repository

* Fix to check only if signed user has forked repo otherwise it will still redirect to wrong page

templates/repo/home.tmpl

@@ -10,7 +10,7 @@
 		<div class="ui secondary menu">
 			{{if .PullRequestCtx.Allowed}}
 				<div class="fitted item">
-					<a href="{{.BaseRepo.Link}}/compare/{{.BaseRepo.DefaultBranch}}...{{.SignedUser.Name}}:{{.BranchName}}">
+					<a href="{{.BaseRepo.Link}}/compare/{{.BaseRepo.DefaultBranch}}...{{if .SignedUser.HasForkedRepo .BaseRepo.ID }}{{.SignedUser.Name}}:{{end}}{{.BranchName}}">
 						<button class="ui green small button"><i class="octicon octicon-git-compare"></i></button>
 					</a>
 				</div>